Researchers at Rice University have developed an energy-efficient nanomaterial for (Rice Lab’s main cause of the hydrogen economy) the hydrogen economy. Using only inexpensive materials, a team from Rice’s Laboratory for Nanophotonics, Syzygy Plasmonics Inc. and Princeton University’s Andlinger Center for Energy and the Environment has developed a catalyst that uses only thermal energy to convert ammonia into flammable hydrogen.
The research follows government and industry investment to develop infrastructure and markets for carbon-free liquid ammonia that will not contribute to greenhouse warming. Liquid ammonia is easy to transport and has a lot of energy, with one nitrogen atom and three hydrogen atoms per molecule. This innovation causes the body to break down these molecules into hydrogen gas, clean burning fuel, and nitrogen gas, which is the largest component of the Earth’s atmosphere. And unlike traditional catalysts, it does not require heat. Instead, it gets energy from light, whether it’s sunlight or incandescent light.
The rate of chemical reactions increases with temperature, and chemical manufacturers have used this for over a hundred years by applying heat to many industries. Burning fossil fuels to raise the temperature of large reactors by hundreds or thousands of degrees creates a huge carbon footprint. Chemical manufacturers also spend billions of dollars each year on propellants – substances that do not react but still speed up reactions under heat.
“Transitional metals such as iron are generally poor heat exchangers,” said co-author Naomi Halas of Rice. “This work shows that they can be effective plasmonic photocatalysts. It also shows that photocatalysis can be done efficiently with low-cost LED photon sources.
“This discovery paves the way for sustainable, low-cost hydrogen that can be produced locally rather than in large, centralized plants,” said Peter Nordlander, also a co-author of the paper at Rice.
The best thermocatalysts are made from platinum and other precious metals such as palladium, rhodium and ruthenium. Halas and Nordlander have spent years developing light-active or plasmonic nanoparticles. Precious metals such as silver and gold are used to make the best items.
Following their 2011 discovery of plasmonic particles that emit short-lived, high-energy electrons called “light carriers”, they discovered in 2016 that hot light carriers can mate particles that create “reactors- hybrid antennae, where one part harvests light. energy and the other part uses energy to make chemical reactions and precision surgery.
Halas, Nordlander, their students and collaborators worked for several years to find a way to turn the ring for the violent reaction in half of the antenna reactors. The new study is the culmination of the project. In it, Halas, Nordlander, former Rice student Hossein Robatjazi, Princeton engineer and physical chemist Emily Carter, and others show that copper and iron antenna-reactor particles are very effective in converting ammonia. The copper part collects the energy of the elements that collect the energy of visible light. Robatjazi, a Ph.D. Alumnus said.
“In the absence of light, the copper-iron catalyst showed about 300 times less reaction than the copper-ruthenium catalysts, this is not surprising because ruthenium is a better thermocatalyst for the reaction a,” said Robatjazi, a Ph.D. said the alumnus of the research group Halas who is currently the chief scientist at Houston-based Syzygy Plasmonics. “Under the light, copper-iron shows similar performance and reactivities as copper-ruthenium.
Syzygy licensed Rice’s antenna-reactor technology, and the study included large-scale testing of the reactor in an existing industrial reactor. In laboratory research at Rice, copper smelters made the metal visible with lasers. Syzygy’s tests showed that the actuators maintain their performance under LED lighting and at a rate of 500 times greater than the laboratory setting.
“This is the first report in the scientific literature to show that photocatalysis with LEDs can produce gram-scale production of hydrogen from ammonia,” Halas said. “This paves the way for the complete conversion of precious metals to plasmonic photocatalysis.”
“Given their potential to reduce carbon emissions from the chemical sector, plasmonic antenna-reactor photocatalysts deserve further study,” Carter added. “These results are a great motivation. They suggest that other combinations of rich metals may be used as catalysts for various chemical reactions.
The research is published online in the journal Science.
